Neuropeptide Y (NPY), first isolated in porcine brain extracts (Tatemoto et. al. Nature 1982, 296, 659), is a 36-aminoacid peptide belonging to the family of pancreatic polypeptides, and is one of the most abundant peptides in the brain and in the central nervous system. In addition, NPY is also distributed in several parts of the peripheral nervous system.
Several studies suggest a significant role of NPY in food ingestion regulation and particularly in food dysfunctions like obesity, anorexia and bulimia. Specifically, NPY is a powerful stimulant of food ingestion. Thus, appetite is significantly increased when NPY is injected directly into the CNS of satiated mice (Clark J. T. et. al. Endocrinology 1984, 115, 427; Levine A. S. et. al. Peptides 1984, 5, 1025; Stanley B. G. et. al. Life Sci. 1984, 35, 2635; Stanley B. G. et. al. Proc. Nat. Acad. Sci. USA 1985, 82, 3940). On the other hand, NPY may play a role in cognitive function regulation, e.g. memory (Flood J. F. et. al. Brain Res. 1987, 421, 280; Redrobe J. P. et. al. Brain Res. 1999, 848, 153), and be active in anxiety (Heilig M. et. al. Reg. Peptides 1992, 41, 61) and depression (Heilig M. et. al. Eur. J. Pharmacol. 1988, 147, 465) processes.
NPY is also distributed in the peripheral system. Some studies suggest that it might be involved in hypertensive (Michel M. C: et. al. J. Hypedtens. 1995, 13, 153), and analgesic (Gehlert D. R. Life Sci. 1994, 55, 551) processes, among others.
The endogenous proteins that constitute NPY-binding receptors have been widely studied. Several have been cloned and expressed. At present, six different receptor subtypes, named Y1 to Y6, are recognized (Hispkind P. A. et. al. Annu. Rep. Med. Chem. 1996, 31, 1; Grunemar L. et. al. TiPS Reviews, 15,153). Each NPY receptor subtype is generally associated to a different biological activity. For example, Y2 receptor is involved in the induction of convulsions in rats (Dumont Y. et. al. Brit. J. Pharmacol. 2000, 129, 1075).
The most recently identified receptor is Y5 (Hu et. al. J. Biol. Chem. 1996, 271, 26315). There is evidence that Y5 receptor has a unique pharmacological profile related to food ingestion as compared to the other receptor subtypes. The fact that [D-Trp32]NPY peptide, a selective Y5-receptor agonist with no affinity for Y1 receptor, stimulates food ingestion in rats (Gerald C. et. al. Nature, 1996, 382, 168), supports the hypothesis that Y5 receptor is related to exaggerated food consumption. Consequently, compounds antagonizing Y5 receptor should be effective to inhibit food ingestion and very useful to control diseases like obesity, or nutritional disorders like bulimia or anorexia.
Several NPY5 non-peptidic antagonists have been described. Thus, 2-aminoquinazoline derivatives [PCT Int. Appl. WO 9720823, 1997 (Novartis AG)], sulfonamides [PCT Int. Appl. WO 9719682, 1997 (Synaptic Pharmaceutical Corp.)], pyrazoles [PCT Int. Appl. WO 9824768, 1998 (Banyu Pharmaceutical Co., Ltd)], aminopyridines [PCT Int. Appl. WO 9840356, 1998 (Banyu Pharmaceutical Co., Ltd)], N-aralkyl-2-tetralinamines [PCT Int. Appl. WO 0020376, 2000 (Ortho McNeil Pharmaceutical Inc.)], several amides [PCT Int. Appl. WO 9835957, 1998 (Bayer Corp.)], pyridine and pyrimidine derivatives [PCT Int. Appl. WO 9940091, 1999 (Amgen Inc.)], carbazoles [PCT Int. Appl. WO 0107409, 2001 (Astra Zeneca AB.)], and spiroisoquinolinones [PCT Int. Appl. WO 0113917, 2001 (Bristol-Myers Squibb Co.)], have been prepared.
Benzoxazinone derivatives having biological activity related to NPY receptors are not described in any published work. The only background of benzoxazinone derivatives with biological activity disclosed in literature refer to P2X7-receptor antagonists, useful for the treatment of inflammatory, immune or cardiovascular diseases [PCT Int. Appl. WO 01044213, 2001 (Astrazeneca AB)], to oxytocin receptor antagonists, useful in tocology [PCT Int. Appl. WO 9725992, 1997 (Merck Co., Inc.)], to α1c adrenergic receptor antagonists [PCT Int. Appl. WO 9528397, 1995 (Merck Co., Inc.)], or to pharnesilproteintransferase enzyme inhibitors [PCT Int. Appl. WO 9738665, 1997 (Merck Co., Inc.)].
Painstaking research has led the investigators to synthesize new compounds of general formula (I) with interesting biological properties which render them particularly useful for application in human and/or veterinary therapeutics to treat diseases for which no similar compound has been previously claimed.